/*************************************************************************
 *
 *  Copyright (c) 2023 Fabian Posch
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version 2
 *  of the License, or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor,
 *  Boston, MA  02110-1301, USA.
 *
 **************************************************************************
 */


#ifndef __DB_CLIENT_H__
#define __DB_CLIENT_H__


#include <cstdint>
#include <iostream>
#include <pqxx/pqxx>
#include "db_types.hpp"
#include "task.hpp"

namespace db {

using namespace std;

// some database constants
#define MAX_CON_RETRIES 5

class Connection {

    public:

    Connection(
        db_credentials_t& credentials,
        std::function<void(pqxx::connection *c)> setup_function
    );

    Connection(
        db_credentials_t& credentials
    );

    ~Connection();

    pqxx::connection* get_connection() { return c; };
    void setup() {
        setup_function(this->c);
    }

    bool connect();
    void disconnect();
    bool ensure_connected();
    int find_job(std::string p_name, std::string *f_name);
    JobStatusType get_job_status(std::string job);
    JobStatusType get_task_status(db::uuid_t);

    bool prepare_statements(vector<pair<string, string>> statements);
    bool prepare_statement(std::string name, std::string statement);
    bool unprepare_statement(std::string name);

    // Send request takes an arbitrary request method to the database and wraps error handling
    // around it. It takes a function with an arbitrary set of arguments and the arguments to give
    // that function and returns whatever the function returns.
    // Careful with typing here! C++ doesn't quite do the strictest typing once you go deep like this!
    // The function is defined here as it can be accessed from outside this library and is templated.
    // This means it must be accessible to the compiler at all times. Failing this will cause a linker error.
    template<typename... Args>
    bool send_request(std::function<void(pqxx::work*, Args...)> *db_function, Args... args) {

    retry_send:

        if (!ensure_connected()) {
            cerr << "Could contact database. Broken database connection." << endl;
            return false;
        }

        try {

            pqxx::work txn(*c);

            try {
                // we assume the lambda takes a pointer to a transaction object as first argument
                // and whatever else was given to us as the rest
                (*db_function)(&txn, args...);

                // commit the task to the database
                txn.commit();
            } catch (const exception& e) {

                // if something happened during the transaction, we roll it back
                txn.abort();

                cerr << "Could not complete database operation. Error in execution." << endl;
                cerr << e.what() << endl;

                return false;
            }

        } catch (const pqxx::broken_connection& e) {
            cerr << "Pipe broke during database operation... Retrying..." << endl;
            cerr << e.what() << endl;

            // using a goto here since it'll gracefully retry connection
            goto retry_send;
        }

        return true;
    };

    private:

    db_credentials_t db_credentials;
    pqxx::connection *c;
    std::function<void(pqxx::connection *c)> setup_function;
    bool connected;
};

const vector<pair<string, string>> uplink_statements = {
    {"commit_task", "UPDATE tasks SET t_status = DONE, error = $2, sim_log = $3, sim_trace = $4 WHERE id = $1"}
};

const vector<pair<string, string>> downlink_statements = {
    {"check_open_tasks", "SELECT id FROM tasks WHERE t_status=OPEN LIMIT 1"},
    // TODO add inner join to grab pipeline depth
    {"fetch_task", "SELECT id, job, t_status, t_type, is_reference, reference, max_plf, error, sim_log FROM tasks WHERE id = $1 LIMIT 1"}
};

};

#endif